best hills ranch lake sediment investigation
DESCRIPTION
Best Hills Ranch Lake Sediment Investigation. Danelle Russell Josh Peterson Chris Foster Sarah Richardson. Objectives. Percent Water Rate of Sediment Accumulation Phosphorus Analysis Percent Organic Matter . K-B Core Samples. Extruding 2 cm layers. Percent of Water in Sediment. - PowerPoint PPT PresentationTRANSCRIPT
Best Hills Ranch Lake Sediment Investigation
Danelle RussellJosh PetersonChris Foster
Sarah Richardson
Objectives
• Percent Water• Rate of Sediment Accumulation• Phosphorus Analysis• Percent Organic Matter
K-B Core Samples
Extruding2 cm layers
Percent of Water in Sediment
• An estimate for amount of sediment to remove by suction dredging
• Weigh 1 tsp. wet sediment from each layer• Dry the sediments at 50ºC for 24 hrs in a oven• Reweigh each dried sample • (wet weight - dried weight) = water content
Sediment Accumulation
• 2 cm / 12 years = 0.167 cm / year• (300 cm = deepest point in pond)300 cm / 0.167 = 1796 years for pond to fill in!
Phosphorus Analysis
• P is often a limiting nutrient in aquatic systems (Shindler, 1977)
• Plants that root in sediment primarily uptake P from the sediments (Bristow, 1975; Gabrielson et al., 2984)
• Combined K persulphate, deionized water, soil, pressure, and heat (autoclaved) to detached P from the sediment and put into solution.
• Measured P from each layer of solution using a light spectrophotometer
Organic Matter in Sediment
• OM includes: plants, algae, fungi• Primary source of nutrients for aquatic
vegetation (Wetzel, 2001).
• Use dry sediment• muffle furnace at 550ºC for 3-4 hours
Dry weight – ash weight = organic matter
Water content of soil
10 20 30 40 50 60 70 80 900
2
4
6
8
10
12
14
Water content western half
Midway Middle of lake
% water content
Dept
h (c
m)
20 30 40 50 60 70 800
2
4
6
8
10
12
Water content Eastern half
House Shore Hill Shore% water content
Sedi
men
t Dep
th (c
m)
Organic Matter Content of soil
0 5 10 15 20 25 30 35 400
2
4
6
8
10
Organic matter eastern half
House shore Hill shore
% organic matter
Sedi
men
t Dep
th (c
m)
2 4 6 8 10 12 14 16 18 200
2
4
6
8
10
12
14
Organic content
Midway Middle of lake
% organic content
Dept
h (c
m)
Phosphorus in the Sediment
0.00 2.00 4.00 6.00 8.00 10.00 12.000
2
4
6
8
10
12
14
Sediment phosphorus profile
Phosphorus concentration (g/L)
Soil
dept
h (c
m)
2 2.5 3 3.5 4 4.50
2
4
6
8
10
12
Average Sediment Phosphorus Profile
Eastern half Western half
Phosphorus concentration (g/L)
Dept
h (m
)
Findings:
0-2 cm 2-4 cm 4-6 cm 6-8 cm 8-10 cm 10-12 cm0.00
10.00
20.00
30.00
40.00
50.00
60.00
Depth in sediment
Sedi
men
t TP
(g/m
2)1. Surprisingly little sediment
2. High Phosphorus content
What can we do?
• Phosphorus loading is the problem1. Deal with the phosphorus in the Lake already2. Manage the source of phosphorus
Some measures of removing phosphorus already within the Lake:
Sediment
Removal
Mechanical Dredging
(Not an option)
Suction dredging
• Controlled Removal of Sediment– High Volume Suction Pump
De-water the lake
•Drain during summer months •Use 3” portable gas pumps (2)
•16 days to de-water lake
• $800 to rent 2 pumps (Sun Rentals)
SweepAfter sediment dries sweep to one end
$50 per day for rental (A-Z Rentals)
Remove Sediment
• Haul sediment away– Cost depends on amount of sediment– Also depends on disposal– Possibly find someone to use sediment
• 300 m³ of sediment if top 2 cm are removed.
• Dried sediment should be less due to water content
Issues
• Waterless lake for an amount of time
• Weather– Depends on how much rain
• Well output– Unknown if well can refill lake alone
Before draining
• Contact landowner below dam
Barley Straw
• Use after sediment removal.• Considered a more natural, organic approach.• Used to decrease the algal growth in water.
– Chemical properties of decomposing barley are thought to inhibit the growth of algae.
– May act as a carbon source for microbes. An increase of microbes causes phosphorus to be limited for algal growth.
Barley Straw
• Barley straw must be installed in March or April, before algal growth occurs.
• Takes approximately 6 weeks to decompose.• Barley stuffed loosely into mesh bags.• Anchored in 2 to 5 feet of water with rocks in
bottom of bags.• Suspended in water column with floats in top
of bags.
Barley Straw
• Distribution of straw must be uniform across the lake.
• Good for about 6 months and is taken out of the system in the fall.
• Taking straw out is crucial so as not to add nutrients to the lake.
Amount and Price– It takes about 225 lbs of straw per acre.– 3.7 acres x 225 lbs = 833 lbs– Average price for ½ ton of barley straw is $22.00
Pros and Cons
• Pros• Inexpensive• Can get high school or
college groups to install/remove it.
• Reduction of algae without chemicals.
• Cons• Could promote
macrophyte growth.
• Labor intensive.• Disposal of used
straw messy.
Questions?